www.semargroup.org, www.ijsetr.com ISSN 2319-8885 Vol.03,Issue.13 June-2014, Pages:2930-2936 Performance Analysis of WiMAX at 2.4, 3.5 and 5.8 GHz in Urban, Suburban Areas V. SURESH KRISHNA 1, K. CHANDRASEKHAR 2 1 PG Scholar, Dept of ECE, Sir C. R. Reddy College of Engineering, Andhrapradesh, India. 2 Asst Prof, Dept of ECE, Sir C. R. Reddy College of Engineering, Andhrapradesh, India. Abstract: Deployment of a hybrid wireless and local area network (LAN) system is a feasible solution for smart grid communication. In this paper, a combination of fixed worldwide interoperability for microwave access (WiMAX) at 2.4, 3.5 and 5.8 GHz and Ethernet LAN is proposed for monitoring and control of energy meters in a smart grid. Communication signal quality is an important factor to consider as it directly affects the reliability of the whole monitoring and control system of a smart grid. In this paper, the signal quality in terms of received signal strength indicator (RSSI) and path losses of the WiMAX system is investigated with a laboratory-scale smart grid prototype. Real-time RSSI is recorded and analyzed to develop an analytical model for the WiMAX RSSI transmitting at 2.4, 3.5 and 5.8 GHz. Keywords: WIMAX, RSSI, Path Losses. I. INTRODUCTION People are enjoying wireless internet access for telephony, radio and television services when they are in fixed, mobile or nomadic conditions in present situations. The rapid growth of wireless internet causes a demand for high-speed access to the World Wide Web. To serve the demand for access to the internet anywhere any time and ensure quality of service, the IEEE 2.16 working group brought out a new broadband wireless access technology called WI-MAX meaning Worldwide Interoperability for Microwave Access. WI-MAX is the latest broadband wireless technology for terrestrial broadcast services in Metropolitan Area Networks (MANs). It was introduced by the IEEE 2.16 working group to facilitate broadband services on areas where cable infrastructure is inadequate. It is easy to install and cheap. It provides triple play applications i.e. voice, data and video for fixed, mobile and nomadic applications. The key features of WI-MAX including higher bandwidth, wider range and area coverage, its robust flexibility on application and Quality of Services (QoS) attract the investors for the business scenarios. Now the millions of dollar are going to be invested all over the world for deploying this technology. Broadband Wireless Access (BWA) systems have potential operation benefits in Line-of-sight (LOS) and Non-line-of-sight (NLOS) conditions, operating below 11 GHz frequency. This BWA technology is based on Orthogonal Frequency Division Multiplex (OFDM) technology and considers the radio frequency range up to 2-11 GHz and 10-66 GHz. Propagation condition under NLOS is possible by using OFDM, which opens the possibility of reliable and successful communication for wireless broadband. An important feature is an adaptive modulation technique, which depends on Signal to Noise Ratio (SNR).It ensures transmission during difficult condition in propagation or finding weak signal in the receiver-end by choosing a more vigorous modulation technique. In an ideal condition, Wi-MAX recommends up to 75 Mbps of bit rate and range within 50 km in the line of sight between transmitter and receiver. But in the real field, measurements show far differences from ideal condition i.e. bit rate up to 7 Mbps and coverage area between 5 and 8 km. To reach best results close to those, obtained from measurement it must be taken into account some factors in spreading - path loss, fading, delay spread, Doppler spread, Co-channel interference. In this project, mainly focus on path losses. The Wi-MAX air interface is designed to operate over a range of frequencies from 2.5 to 2.69 GHz, from 3.4 to 3.6 GHz and from 5.725 to 5.850 GHz. The channel bandwidth can be an integer multiple of 1.25 MHz, 1.5MHz and 1.75 MHz with a maximum of 20 MHz, The licensed frequency 2.5 GHz is used in America and 3.5 GHz is used in Europe, Asia, and Africa. II. PERFORMANCE PARAMETERS Prior to the deployment of wireless communication, its network performance has to be evaluated to ensure efficiency and reliability. There is very little research done in the area of wireless network performance for communication in smart grids. Network performance parameter such as path loss indirectly affects the quality of signal of the wireless network. A. Path Loss Path loss arises when an electromagnetic wave propagates through space from transmitter to receiver. The power of signal is reduced due to path distance, reflection, Copyright @ 2014 SEMAR GROUPS TECHNICAL SOCIETY. All rights reserved.
diffraction, scattering, free-space loss and absorption by the objects of environment. It is also influenced by the different environment (i.e. urban, suburban and rural). Variations of transmitter and receiver antenna heights also produce losses. In our thesis we mainly focus on path loss issue. In general it is expressed as: B. Received Signal Strength Indicator (RSSI) In telecommunications, received signal strength indicator (RSSI) is a measurement of the power present in a received radio signal. RSSI is a generic radio receiver technology metric, which is usually invisible to the user of the device containing the receiver, but is directly known to users of wireless networking of IEEE 2.11 protocol family. RSSI is an indication of the power level being received by the antenna. Therefore, the higher the RSSI number, the stronger the signal. RSSI can be used internally in a wireless networking card to determine when the amount of radio energy in the channel is below a certain threshold at which point the network card is clear to send (CTS). Once the card is clear to send, a packet of information can be sent. The Received Signal Strength Indicator (RSSI) or Signal Strength is a measure of how strong the most recent signal was when it reached its destination. The RSSI value ranges from 0 to 255. Higher RSSI values indicate a stronger signal. Reliable communication can best be achieved with RSSI values greater than 70. If the RSSI is too low the wireless communications may become intermittent or fail entirely. The received signal strength for Okumura model, Hat model and COST-231 model can be calculated as V. SURESH KRISHNA, K. CHANDRASEKHAR (1) P r = P t + G t + G r PL A (2) Pr is received signal strength in dbm. Pt is transmitted power in dbm. Gt is transmitted antenna gain in dbm. Gr is received antenna gain in dbm. PL is total path loss in dbm. A is connector and cable loss in dbm. In this work, connector and cable loss are not taken into consideration III. PATH LOSS MODELS In our paper, we analyze five different models which have been proposed by the researchers at the operating frequency of 2.5., 3.5 and 5.8 GHz. We consider free space path loss model which is most commonly used idealistic model. We take it as our reference model; so that it can be realized how much path loss occurred by the others proposed models. A. Free Space Path loss Model Free Space Path Loss Model (FSPL) Path loss in free space PLFSPL defines how much strength of the signal is lost during propagation from transmitter to receiver. FSPL is diverse on frequency and distance. The calculation is done by using the following equation. P LFSPL = 32.45 + 20 log10 (d) + 20log10 (f) (3) Where, f: Frequency [MHz] d: Distance between transmitter and receiver [m] Power is usually expressed in decibels (dbm). B. Stanford University Interim (SUI) Model IEEE 2.16 Broadband Wireless Access working group proposed the standards for the frequency band below 11 GHz containing the channel model developed by Stanford University, namely the SUI models. The SUI model describes three types of terrain; they are terrain A, terrain B and terrain C. Terrain A can be used for hilly areas with moderate or very dense vegetation. This terrain presents the highest path loss. In our paper, we consider terrain A as a dense populated urban area. Terrain B is characterized for the hilly terrains with rare vegetation. This is the intermediate path loss scheme. We consider this model for suburban environment. Terrain C is suitable for flat terrains or rural with light vegetation, here path loss is minimum. The basic path loss expression of The SUI model with correction factors is presented as for d> d0 PL = A + 10* log 10 (d/d o ) + X f +X h + s (4) Where the parameters are d: Distance between BS and receiving antenna [m], d 0: [m] Xf: Correction for frequency above 2 GHz X h : Correction for receiving antenna height[m]s: Correction for shadowing: Path loss exponent The parameter A is defined as A= 20 log 10 (4πd o /λ) And the path loss exponent γ is given by γ = a bh b + (c/h b ) Where, the parameter hb is the base station antenna height in meters. This is between 10 m and m. The constants a, b, and c depend upon the types of terrain. TABLE I: Parameters for Different Type of Terrains For Sui Model Parameter Terrain A (Urban area) Terrain B (Suburban area) Terrain C (Rural area) a 4.6 4.0 3.6 b [1/m] 0.0075 0.0065 0.005 C [m] 12.6 17.1 20 C. Hata-Okumura extended model or ECC-33 Model One of the most extensively used empirical propagation models is the Hata-Okumura model, which is based on the Okumura model. This model is a well-established model for the Ultra High Frequency (UHF) band. Recently, through the ITU-R Recommendation P.529, the International Telecommunication Union (ITU) encouraged this model for further extension up to 3.5 GHz. PL = A fs + A bm -G b -G r (5)
Performance Analysis of WiMAX at 2.4, 3.5 and 5.8 GHz in Urban, Suburban Areas A fs : Free space attenuation [db] A BM : Basic median path loss [db] G B : Transmitter antenna height gain factor G r : Receiver antenna height gain factor These factors can be separately described and given by as A fs = 92.4 + 20 log 10 (d) + 20 log 10 (f) A bm =20.41+9.83 log 10 (d)+7.894log 10 (f)+9.56[log 10 (f)] 2 G b = log 10 (h b /200) {13.958 + 5.8[log 10 (d)] 2 } When dealing with gain for medium cities, the Gr will be expressed in G r = [42.57 + 13.7 log 10 (f)][log 10 (h r ) 0.585] For large city G r = 0.759h r 1.862 Where, d: Distance between transmitter and receiver antenna [km] f: Frequency [GHz] hb: Transmitter antenna height [m] hr: Receiver antenna height [m] D. COST 231 Walfish-Ikegami (W-I) Model This model is a combination of J. Walfish and F. Ikegami model. The COST 231 project further developed this model. Now it is known as a COST 231 Walfish- Ikegami (W-I) model. This model is most suitable for flat suburban and urban areas that have uniform building height.among other models like the Hata model, COST 231 W-I model gives a more precise path loss. This is as a result of the additional parameters introduced which characterized the different environments. It distinguishes different terrain with different proposed parameters. The equation of the proposed model is expressed in For LOS condition PL LOS = 42.6 + 26 log (d) + 20 log (f) (6) And for NLOS condition PL NLOS = L FSL + L rts + L msd for urban And suburban L FS if L rts + L msd > 0 (7) Where LFSL= Free space loss L rts = Roof top to street diffraction L msd = Multi-screen diffraction loss IV. CALCULATION PARAMETERS Values of parameters are given below TABLE II: CALCULATION PARAMETERS Parameters Values Distance from transmitter 5km to receiver Transmitter height 50m Urban area 30m Suburban area 20m Rural area Receiver antenna height 2m to 10m Operating Frequency 2.5,3.5 and 5.8GHz Average building height 15m Building to building 50m distance Street width 25m V. CALCULATION RESULTS A. Results from calculations for suburban area Figure 1, 2 and 3; show the results from calculations for suburban area: 70 170 6m receiver antenna height in suburban environment ks-ecc 33 b+- freespace Figure 1. Comparison of path loss models for suburban area at 3.5GHz. 1 6m receiver antenna height in suburban environment ks-ecc 33 b+- freespace 60 Figure 2. Comparison of path loss models for suburban area at 5.8GHz. 170 6m receiver antenna height in suburban environment ks-ecc 33 b+- freespace 70 Figure 3. Comparison of path loss models for suburban area at 2.4GHz.
B. Results from calculations for urban area Figure 4, 5 and 6; show the results from calculations for urban area: 170 6m receiver antenna height in urban environment ks-freespace b+- ECC 33 V. SURESH KRISHNA, K. CHANDRASEKHAR Figure4. Comparison of path loss models for urban area at 3.5GHz. Figure7.RSSI of COST- 231 Hata model (Therotical and practical) for 2.4GHz 200 1 6m receiver antenna height in urban environment ks-freespace b+- ECC 33 Figure5. Comparison of path loss models for urban area at 5.8GHz. Figure8. RSSI of COST- 231 Hata model (Therotical and practical) for 3.5GHz. 6m receiver antenna height in urban environment ks-freespace b+- ECC 33 70 Figure6. Comparison of path loss models for urban area Figure9. RSSI of COST- 231 Hata model (Therotical at 2.4GHz. and practical) for 5.8GHz.
Performance Analysis of WiMAX at 2.4, 3.5 and 5.8 GHz in Urban, Suburban Areas Figure13. RSSI of Hata- okmura model for 2.4GHz Figure12. RSSI of SUI model for 2.4GHz Figure10. RSSI of Hata- okmura model for 3.5GHz Figure13. RSSI of SUI model for 3.5 GHz Figure11. RSSI of Hata- okmura model for 5.8GHz Figure14. RSSI of SUI model for 5.8 GHz
Figure15. RSSI of COST-231 W-I model for 2.4GHz. Figure16. RSSI of COST-231 W-I model for 3.5 GHz. Figure17. RSSI of COST-231 W-I model for 5.8 GHz. Figure 7 to 17; show the results from calculations for RSSI of COST- 231 Hata model (Therotical and practical) and RSSI of SUI model. V. SURESH KRISHNA, K. CHANDRASEKHAR VI. CONCLUSION Our comparative analysis indicate that due to multipath and NLOS environment in urban area, all models experiences higher path losses compare to suburban and rural areas. Moreover, we did not find any single model that can be recommended for all environments. We can see in urban area, the SUI showed the lowest path loss as compared to other models. Alternatively, the ECC-33 model showed the heights path loss. In suburban area the SUI model showed quite less path loss compared to other models. On the other hand, COST231 W-I model showed heights path loss as showed in urban area. In rural area, we can choose different models for different perspectives. If the area is flat enough with less vegetation, where the LOS signal probability is high, in that case, we may consider LOS calculation. Alternatively, if there is less probability to get LOS signal, in that situation, we can see COST-Hata model showed the less path loss compare to SUI model and Ericsson model especially in 10 m receiver antenna height. But considering all receiver antenna heights SUI model showed less path loss whereas COST-Hata showed higher path loss. If we consider the worst case scenario for deploying a coverage area, we can serve the maximum coverage by using more transmission power, but it will increase the probability of interference with the adjacent area with the same frequency blocks. On the other hand, if we consider less path loss model for deploying a cellular region, it may be inadequate to serve the whole coverage area. Some users may be out of signal in the operating cell especially during mobile condition. So, we have to trade-off between transmission power and adjacent frequency blocks interference while choosing a path loss model for initial deployment. VII. REFERENCES [1] V.S. Abhayawardhana, I.J. Wassel, D. Crosby, M.P. Sellers, M.G. Brown, Comparison of empirical propagation path loss models for fixed wireless access systems, 61th IEEE Technology Conference, Stockholm, pp. 73-77, 2005. [2] Josip Milanovic, Rimac-Drlje S, Bejuk K, Comparison of propagation model accuracy for WiMAX on 3.5GHz, 14th IEEE International conference on electronic circuits and systems, Morocco, pp. 111-114. 2007. [3] Joseph Wout, Martens Luc, Performance evaluation of broadband fixed wireless system based on IEEE 2.16, IEEE wireless communications and networking Conference, Las Vegas, NV, v2, pp.978-983, April 2006. [4] V. Erceg, K.V. S. Hari, M.S. Smith, D.S. Baum, K.P. Sheikh, C. Tappenden, J.M. Costa, C. Bushue, A. Sarajedini, R. Schwartz, D. Branlund, T. Kaitz, D. Trinkwon, "Channel Models for Fixed Wireless Applications," IEEE 2.16 Broadband Wireless Access Working Group, 2001. [5] Empirical Models, [Online] Available: http:// en.wikipedia.org/wiki/empirical_model [Accessed April 18, 2009]. [6] D. Pareek, The Business of WiMAX, Chapter 2 and Chapter 4, John Wiley, 2006.
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